What is the difference between MCB and MCCB circuit breakers and what are the differences when conducting life tests?

MCB (Miniature Circuit Breaker) and MCCB (Molded Case Circuit Breaker) are both commonly used low voltage circuit breakers that play an important role in circuit protection and electrical safety. Although their functions are similar, they have a number of differences in terms of design, application and mechanical life testing.

Firstly, MCBs are primarily used for short circuit and overload protection at low currents (usually below 100 amps), while MCCBs are primarily used for short circuit and overload protection at high currents (usually above 100 amps). This is due to the different construction designs and materials used in MCBs and MCCBs to suit different currents and loads. Secondly, MCBs typically use electronic components such as reeds and thermal relays for protection, whereas MCCBs use mechanical devices such as thermomagnetic protectors for protection. This is what makes them different for mechanical life testing.

When conducting mechanical life tests, both the MCB and MCCB need to be tested for parameters such as the number of times they open and close, contact resistance and protection function. The difference is that due to the lower operating and rated currents of the MCB, they should be tested at lower currents and loads, usually below 100A. MCCBs, on the other hand, have higher operating and rated currents and should be tested at higher currents and loads, usually above 100A.

In addition, because of the more durable mechanical construction and materials of MCCBs, their mechanical life tests usually require testing for longer periods of time and a greater number of openings and closings.
Overall, the differences between MCBs and MCCBs when it comes to mechanical life testing are mainly in the size of the loads tested and the time and number of tests performed. This also reflects the differences in their application and design. When selecting and applying circuit breakers, the MCB or MCCB should be selected according to the specific circuit and load requirements and the corresponding mechanical life tests carried out to ensure their performance and reliability.